Carly Rae Jepsen, The Wanted, Mindless Behavior, Owl City, X Factor's Rachel Crow, GLEE's Matthew Morrison and many more came to the USTA Billie Jean King National Tennis Center in Flushing, New York City on Saturday to support the Annual Arthur Ashe Kids' Day. Jepsen took over center court, performing her No. 1 single "Call Me Maybe." The number prompted a spontaneous flash mob as several of the pro tennis players as well as Max George, Jay McGuiness, Siva Kaneswaran, Tom Parker, Nathan Sykes, Matthew Morrison and Mindless Behavior ran out to join the Canadian singer and show off their dance moves. Check out photos from the event below!

Arthur Ashe Kids' Day is an annual tennis/children’s event that takes place in the end of August at the United States Tennis Association at Arthur Ashe Stadium in Flushing Meadows, Queens, New York. It is sponsored by the Hess Corporation, IBM, and USTA. This event also begins the U.S. Open, which officially starts one day later.

This event is a celebration of the memory of Arthur Ashe, who died of AIDS in 1993, and of his efforts to help young people through tennis. Kids’ Day began in 1993, the year that Ashe died.